Biology 2b03 structural component of cell sensors for environmental changes and mechanisms for relaying info to cell enzymes, catalysts for chemical reactionns gene regulation signalling molecules between cells molecular motors organelle identity and function. Polypeptide to protein - amino acids and chemical interactions. Protein structure structure of protein related to function. Solubility - refers to ability of molecule to transiently bond with water via hydrogen bonding this is thermodynamically favourable. Hydrophilic molecule: is charge-polarized and can h-bond with water. Hydrophobic molecule: not electrically polarized and unable to form h-bonds, so water repels them in favour of bonding with itself. Aromatic aminos acids - phenylalanine (f), tyrosine (y), tryptophan (w) Note: tyrosine is both hydrophobic and hydrophilic due to it"s -oh group. Aliphatic amino acids - alanine (a), valine (v), isoleucine (i), leucine (l), methionine (m) Hydrophilic amino acids these are charge-polarized and capable of hydrogen bonding hydrophilic amino acids are charged (ionized) at ph = 7.